3 It is possible that an eclipse observed at Ilimsk in Middle Siberia by Chirikoff is thus erroneously referred to.
Euler, who had access to the archives of the Admiralty College, while engaged on a Geography of Russia, mentions (Philos. Trans., No. 482, p. 421) that he was informed that Bering observed an eclipse "at Kamchatka." This letter of Euler's is copied by Campbell in Harris' Voyages (vol. II, Book III, p. 1024) and the expression "at Kamchatka" has led to the statement that these observations were made at the fort or village of Lower Kamchatka. This is an error since Bering gives no longitude for the fort in his table of geographical positions. It must be remembered that the name Kamchatka at that period was applied not merely to the peninsula as at present, but also to the whole region of northeastern Siberia, the governor of Kamchatka being located at Okhotsk. So to come within the probable meaning of the phrases used by Middendorf and Euler it is only necessary to suppose that the observations were made somewhere in that region. Lauridsen (Danish edition, note 34, p. 186) refers to a paper of Struve (Bull. phys.-math. Acad. St. Petersb., I, 1842, p. 290) containing a table of geographical positions in Russia, in connection with these alleged observations of Bering. An examination of Struve's paper does not bear out the implication of Lauridsen's reference, as Struve not only makes no mention whatever of Bering's observations there but specifically states that the first observations of precision made in this part of Siberia were those of Krassilnikoff who accompanied Bering's second expedition in 1741. It would seem extraordinary that a determination so important for geography as that of Bering and his companion should be unknown to so distinguished an astronomer as Struve who must have had access to all the archives of the early explorations by Russia. But it may be perhaps accounted for by the facts that Bering's observations were necessarily of a very rough and primitive character—as it is certain he had no instruments of precision; and that, for that reason, they were not received with entire confidence; so that Struve may have considered them insufficiently exact to be included with those of Krassilnikoff and others made with more modern appliances.
From the note in regard to the eclipses which is kindly contributed by Mr. Marcus Baker and from the other circumstances, it is evident that if Bering and his party made the observations alluded to, the eclipses noted were the partial eclipse of Feb. 25 (local calendar), 1728, of which he might have observed the last contact, or the total eclipse of Feb. 14, 1729, of which he might have observed the first contact and the totality. At the time of the last eclipse he was at Lower Kamchatka post, and as, in the list of positions handed in with his Report in 1730, no longitude is entered for this locality, it would seem that choice is reduced to the first of the two mentioned; which occurred when Bering was either at Bolsheretsk or on his way from that place to Lower Kamchatka, which he reached about a month later. Campbell's table of positions is credited by him to the year 1728, but my own opinion is that it was really derived (with various errors, interpolations, etc.) from Bering's table of 1730.
The ordinary method of getting the longitude of a place, and that upon which Bering originally depended, as his itinerary table shows, was by a continuous record of the distances and directions traveled from a point of known longitude. This record would afford the data from which the distance on a mean parallel, by means of a traverse table, could be computed. Laborious, imperfect, and slow as it was, it was the only sure reliance of the traveler in those days. Whether Bering observed an eclipse or not, it is certain that his original dependence was upon his itinerary, that his report was based upon that and that this part of his work was done as well as the nature of the method would permit. His silence about the eclipse may be due to the fact that he depended not upon astronomical but upon pedometric observations, to which the eclipse may have afforded some corrections. At any rate the pedometric determination of the distance between Tobolsk and Okhotsk or the peninsula of Kamchatka was in itself a tremendous undertaking.
I find by a rough calculation from Bering's data that the longitude resulting from his itinerary from Tobolsk to Okhotsk is 77° 36' E. The distance in a straight line is about 2,390 miles, but by the route Bering traveled the distance is a little more than 3,746 miles. The longitude in Bering's List of Positions is 76° 07', which differs from the pedometric measurement by 1° 29' (or about 45 miles). On Bering's map, Okhotsk is located in longitude 74° 30' E. of Tobolsk, while the most modern observations for Okhotsk put it in 142° 40' E. of Greenwich or 75° 40' E. of Tobolsk. So that Bering's pedometric measurement was nearly 60 miles in excess; his revised table (as corrected by the eclipse?) 27 miles in excess; and his map about 30 miles in error in the opposite direction. These discrepancies show the inexactness of the methods then in vogue and also that the pedometric method was not very much worse than the others in its results. Although there are several typographic or other errors in his table of itinerary which render exact comparisons impossible, it may be said that the error of the pedometric method, including the passage by sea from Okhotsk to Kamchatka, averages about two degrees or sixty geographical miles. In the cases of Okhotsk and Bolsheretsk the error is one of excess; in the case of the cape at the mouth of the Kamchatka river and of the turning point of the expedition north of Bering Strait, the result is too small by about the same amount.
That his chart and his revised list of positions should differ as they do, is quite as likely the result of the careless way in which the minutiæ of such work were generally regarded at that day, as to any difference of date, or of intentional modification.
To conclude our review of the instrumental means and methods then in use, it may be said that the compasses in use at that day were comparatively roughly made and more or less inaccurate. The variation was determined in a given latitude by the azimuth of the Polestar or the sun at setting observed by means of sights attached to the rim of the compass, which was a method accurate enough for the general purposes of navigation. The distance run was measured on shipboard by the log which was in about the same form and perfection as at present, being a very ancient invention.
The survey of a general coast-line was made by compass bearings on prominent points, repeated from successive stations, the distances of the ship's course being determined by the log and the courses by compass, with corrections for current and the variation. The lines thus obtained were checked by latitude observations made with Davis' backstaff when the weather permitted.
Apart from any of the methods mentioned it seems to have been overlooked that Bering might have corrected the longitudes of the N.E. Siberian coast by the ordinary dead reckoning kept on board his vessel, provided he started by adopting the longitude for the southern part of Kamchatka peninsula which was in common use on many of the charts of his day. Though it is true that the maps of that part of Siberia north and northeast from the Okhotsk sea were many degrees in error in the longitude, this observation does not hold good in regard to the southern end of Kamchatka. The work of the Jesuit fathers in China had already determined fairly well the position of China and Korea, while rude outlines of the northern islands of Japan, Sakhalin, the Kuriles and the south end of Kamchatka, were added to these on maps of Asia. The outlines are often very incorrect but it is quite evident what is intended. In nearly all early maps of this region which I have been able to consult, as for instance those of N. de Witt, I have found the south end of Kamchatka in approximately correct longitude. For instance, in the Novissimae Ephemerides of Manfredio, published at Bonn the same year that Bering left St. Petersburg, and which might well have been sent to him before he sailed, we find two charts of the paths of solar eclipses (Plates ii and iii). On these charts the meridian of 180° from Ferro passes across what is unmistakably the south end of Kamchatka, though northeastern Siberia remains a blank. This would be a sufficient starting point and is quite as correct as Bering's determinations; in fact is within a few miles of the modern longitudes for the same part of the peninsula. Dead reckoning along the shores of the peninsula, corrected by latitude observations, would have done all that was necessary to correct the meridian without observing any lunar eclipse, provided the surveyor started with such an assumption as Manfredio's or De Witt's charts supply.
SOURCES OF INFORMATION.